Disposable diaper

ABSTRACT

A disposable multi-layer diaper of high absorptive capacity and improved feel is provided which comprises as a first layer, to be brought into contact with an infant&#39;&#39;skin, a porous, fibrous, nonwoven bonded facing web of controlled wettability made of short cellulosic fibers and long fibers at a given overall concentration. The outer face of the facing layer is characterized by a blend of long and short fibers, with the concentration of long fibers being in excess of the overall concentration, while the inner face of the facing layer is also characterized by a blend of long and short fibers, with the concentration of short fibers being in excess of the overall concentration. The outer face of the facing layer has a sufficient amount of long fibers to give the diaper improved feel and wearing characteristics. The concentration of short cellulosic fibers gradually, and preferably substantially uniformly, increases from the outer face to the inner face of the facing layer to provide a gradually increasing degree of wettability for preferentially drawing the urine away from the outer face, through the facing layer and into a second layer, in juxtaposition to the facing layer. The second layer is a highly porous, loosely compacted completely cellulosic batt having greater wettability than that of the facing web. A third layer, integral with the second, is a paper-like, densified, highly compacted layer of the same cellulosic material as the second layer but of substantially smaller average pore size and which is selectively thickened in certain areas. The final layer is an impervious backing sheet adhered to the densified layer over a widely distributed area of adhesion.

United States Patent [1 1 Mesek et al.

[ Oct. 30, 1973 DISPOSABLE DIAPER 1nventors:Fredei-ick 1 Mesek, '7 InGrove; Virginia L. Repke, Oak Forest, both of III.

[73] Assignee: Johnson & Johnson, New

Brunswick, NJ.

[22] Filed: June 7, 1972 [21] Appl. No.: 260,557

Primary ExaminerCharles F. Rosenbaum 1 Attorney-Michael Q. Tatlow et al.

[57] ABSTRACT A disposable multi-layer diaper of high absorptivecapacity and improved feel is provided which comprises as a first layer,to be brought into contact with an infantskin, a porous, fibrous,nonwoven bonded facing web of controlled wettability made of shortcellulosic fibers and long fibers at a given overall concentration. Theouter face of the facing layer is characterized by a blend of long andshort fibers, with the concentration of long fibers being in excess ofthe overall concentration, while the inner face of the facing layer isalso characterized by a blend of long and short fibers, with theconcentration of short fibers being in excess of the overallconcentration. The outer face of the facing layer has a sufficientamount of long fibers to give the diaper improved feel and wearingcharacteristics. The concentration of short cellulosic fibers gradually,and preferably substantially uniformly, increases from the outer face tothe inner face of the facing layer to provide a gradually increasingdegree of wettability for preferentially drawing the urine away from theouter face, through the facing layer and into a second layer, injuxtaposition to the facing layer. The second layer is a highly porous,loosely compacted completely cellulosic batt having greater wettabilitythan that of the facing web. A third layer, integral with the second, isa paper-like, densified, highly compacted layer of the same cellulosicmaterial as the second layer but of substantially smaller average poresize and which is selectively thickened in certain areas. The finallayer is an impervious backing sheet adhered to the densified layer overa widely distributed area of adhesion.

10 Claims, 4 Drawing Figures DISPOSABLE DIAPER BACKGROUND OF THEINVENTION Disposable diapers have met with increased commercialacceptance in recent years primarily because of their convenience, asopposed to cloth diapers, which need to be laundered once soiled. Manydifferent constructions have been proposed and used, and some have metwith widespread commercial success in spite of certain inadequacies infunctional properties.

One of the most serious prior art problems has been the inability toprovide a suitable construction that would keep moisture away from thesurface of the diaper which comes into contact with the infants skin andthereby avoid skin irritation and infection. Commonly assigned Mesek etal.'U.S. Pat. No. 3,612,055 discloses several diaper constructions thatfunction extremely well in keeping moisture away from an infants skin,while at the same time handling a full volume discharge of urine.

These functions are accomplished by a multi-layer diaper comprising, inorder, a fibrous facing layer in the form of a substantially homogeneousblend of short and long fibers which is to be brought into contact withthe infants skin, a layer of highly porous, loosely compacted cellulosicbatt, a paper-like densified, highly compacted cellulosic fibrous layerintegral with the loosely compacted batt and an impervious backing sheetadhered to the densified layer throughout the interface therebetween.The facing layer is of porous construction and its fibers have lesswettability for water than the fibers of the loosely compacted batt,resulting in a tendency for liquid to flow from the facing web into thebatt. The densified fibrous layer has a smaller average pore size thanthe loosely compacted batt, resulting in a tendency for liquid to flowpreferentially from the batt into the underlying densified layer ratherthan to other areas of the batt, thus tending to restrict wetting in thebatt to an area of moderate size. Liquid flowing into the densifiedlayer tends to spread laterally because of its wicking action and liquidwhich might pass through the densified layer during discharge (when flowis rapid) is held back by the impervious backing sheet for sufficienttime to permit absorption to take place. Liquid in excessjof theabsorptive capacity of the densified layer is forced back by theimpervious layer into the dry portion of the loosely compacted batt,thus utilizing the additional absorptive capacity therein.

Since facing layers in diapers of the type disclosed in theabove-mentioned patent have substantially the same amount of shortcellulosic fibers adjacent the outer face thereof as adjacent the innerface, there is essentially no wettability difference within'the facinglayer itself, with the result that the diaper is dependent, at least tosome degree, upon the increased wettability of the fibrous batt toretain urine away from the outer surface of the facing layer.

Webs that can be used as a facing layer in diapers as disclosed in theabove-mentioned patent can be formed by an air laying technique. Recentimprovements have been made in such techniques, such as for example, theimprovements disclosed and claimed in commonly assigned, copending Ruffoet al. application Ser. No. 108,546 filed Jan. 21, 1971, the disclosureof which is hereby incorporated herein by this reference. Briefly, oneof the air laying techniques disclosed therein includes the steps offeeding fibers of two different types to separate fiber opening means ata given feed rate to provide the subseqently formed web with a givenoverall concentration of the different type fibers, individualizingfibers from said separate fiber sources, suspending the fibers from eachsource in separate gaseous streams, impelling the gaseous streams atleast initially toward one another and combining said streams to form asingle combined carrier stream wherein the fibers from each gaseousstream intermix with one another with the total gas to total fibervolume ratio being at least 12,000zl in the combined gaseous carrierstream, and condensing the entrained and individualized fibers from saidcombined stream to form a random nonwoven web. At gas to fiber volumeratios above 12,000:l the fibers in the individual streams are spacedsufficiently from one another that if streams are brought together at anangle without substantial diminution in the velosity of the streams,fibers in each stream can cross over the oncoming fibers to form anonwoven product wherein the product is characterized by having aconcentration of at least one fiber type on one face of the product inexcess of the overall concentration and a concentration of at least onedifferent fiber type on the other face of the product in excess of theoverall concentration, with a transition zone between the faces suchthat the concentration of each fiber type gradually diminishes away fromthe face having the maximum concentration for that fiber type to theopposite face.

SUMMARY OF THE INVENTION In accordance with this invention, a diaper isprovided which retains all of the advantageous functionalcharacteristics of the diapers disclosed in the abovementioned patent,while at the same time providing at no increase in cost, (1) improvedfeel and resultant increased comfort to the infant, and (2) a graduallyincreasing wettability gradient within the facing layer to promote flowof urine through the facing layer and into the batt, thereby a relativedry surface in contact with the infants skin.

These improved functions are accomplished in a multi-layer diaper whichincludes in order (1) a waterimpervious backing sheet, (2) anintermediate layer comprised entirely of short cellulosic fibers thatare loosely compacted throughout a major portion of the batt and whichare densified at one side of the batt to provide an integral paper-likeskin adjacent the backing sheet, and (3) a facing layer that is formedof long or textile length fibers and short cellulosic fibers, with thegreatest concentration of long fibers being adjacent the outer face ofthe facing layer, and with the concentration of short cellulosic fibersgradually increasing from the outer face to the inner face adjacent thebatt. It is the concentration of long fibers adjacent the outer surfaceof the facing layer that gives the diaper improved feel and whichresults in greater comfort to the infant. The concentration of longfibers at the outer surface also effectively prevents, or at leastminimizes, any tendency of the short cellulosic fibers to dust from thefacing layer, while at the same time strengthening the outer portion ofthe facing layer.

The short cellulosic fibers are at maximum concentration at the innerface of the facing layer, and the concentration of short cellulosicfibers most preferably substantially uniformly increases inconcentration from the outer face of the facing layer to the inner facethereof. Because the individual short cellulosic fibers are morewettable than the individual long fibers, there is a gradual increase inwettability throughout the cross-sectional thickness of the facing layerthat is substantially directly proportional to the concentration of theshort cellulosic fibers. As noted above, the wettability gradient withinthe facing layer itself promotes, or enhances, passage of urine throughthe facing layer and into the even more wettable, unbonded looselycompacted, cellulosic fibrous portion of the batt layer. The facinglayer may be formed in accordance with the teachings in theabove-mentioned Ruffo et al. application. By using this process, anyunground or compacted pulp particles are confined to the interior of thediaper.

BRIEF DESCRIPTION OF THE DRAWINGS OF FIG. 1 is a perspective view, withcertain portions broken away, of an open unfolded diaper in accordancewith this invention;

FIG. 2 is an enlarged partial cross section of the diaper of FIG. 1,taken generally along line 2-2;

FIG. 3 is a perspective view on a reduced scale of the diaper in itsconfiguration after being put on an infant; and

FIG. 4 is a simplified schematic view of the production line on whichthe diaper is made.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail a preferred embodiment of the invention, with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the invention to the embodiment illustrated. The scope of theinvention will be pointed out in the appended claims.

Referring to the drawings, and particularly to FIGS. 1 and 2, the diaperassembly 10, when fully opened and laid out flat, comprises a lowermostwater-impervious sheet 12 which is rectangular in shape, a highlywaterabsorbent fibrous pad, or batt 14, which is also rectangular inshape, but smaller than the impervious sheet and centrally disposedthereon, and an overlying facing layer 16 of fibrous material, which isalso rectangular in shape, equal in dimension, and coterminous with theimpervious sheet and in contact therewith in the marginal portions ofthe diaper extending peripherally beyond the absorbent pad, i.e., in theportions 16b and 12b of facing layer 16 and impervious sheet 12,respectively. The batt 14 has a continuous paper-like densified highlycompacted lowermost fibrous layer 18 that includes spaced, parallelthickened densified portions 19 in the form of parallel lines thatextend completely through the cross-sectional thickness of the batt.Densified layer 18 is adhered to the impervious sheet by bead lines ofadhesive 22 substantially throughout the inter face therebetween.Marginal portions 16b and 12b are also adhered to each other by beadlines 22.

In the preferred embodiment of the invention, moisture impervious sheetl2 is formed of polyethylene having a thickness of approximately 0.001inch. The sheet may be smooth, or may be embossed to improve its drapeand feel. Other suitable flexible moisture impervious sheets may be usedin accordance with the invention, such as, for example, polyethyleneterephthalate sheets having a thickness of about 0.0005 inch.

Batt 14 is formed of loosely compacted short cellulose fibers, such aswood pulp fibers, or cotton linters, or mixtures thereof, which areprimarily held together by interfiber bonds requiring no added adhesive,as is known in the art. Briefly, this batt is a low bulk densitycoherent web of loosely compacted cellulose fibers preferably comminutedwood pulp fibers in the form of so-called fluff.

The term short fibers, as used herein, refers to fibers less than aboutone-fourth inch in length, in contrast to long fibers, staple lengthfibers or textile length fibers which are longer than about one-fourthinch in length, and generally are between about A and 2% inches inlength. The former are substantially less costly than the latter. theclassification of fibers by length may be carried out by the ClarkClassification procedure described in the test manual of The TechnicalAssociation of Pulp and Paper Industry (TAPPI- T233 SU64).

The paper-like densified layer 18 of batt 14 is formed by a slightmoistening of one surface of the batt followed by the application ofpressure thereto. The nature of the batt and of its densified layer andthe method of producing the same are described in US. Pat. No.3,017,304, dated Ian. 16, 1962. The thickened densified portions 19 areformed by further compression of batt 14 while it is still moist, aswill hereinafter appear.

The composite density of batt 14, including its densified layer 18,should be above about 0.07 gm./cc. and preferably between about 0.10 and0.15 gm./cc. The foregoing density values are applicable to the diaperas produced. In storage and handling, the loft or thickness of the battis increased to some extent, resulting in lowered densities.

Facing layer 16, on an overall basis, is made of a given concentrationof fibers consisting predominantly of short cellulosic fibers such aswood pulp fibers or cotton linters, in amounts of about 50 to about 98percent, the balance being textile length fibers such as rayon,polyester, cellulose acetate, nylon, etc. Short cellulosic fibers suchas wood pulp fibers or cotton linters are substantially less expensivethan textile length cellulosic fibers such as cotton and rayon, andsince low cost is a factor which is of substantial importance, it isdesired to use as large an amount of short cellulosic fibers as isconsistent with strength requirements.

Facing layer 16 is preferably formed by an air laying process, such asfor example, the process disclosed in the above-mentioned Ruffo et alapplication, to produce a web having opposed outer and inner major faces15 and 17, respectively, with face 15 being characterized by aconcentration of staple length fibers in excess of the overallconcentration, and with face 17 being characterized by a concentrationof short cellulosic fibers in excess of the overall concentration. Theterm faces, as used herein, means that portion of the facing layer whichextends inwardly from one outer major surface to approximatelyone-fourth of the total corsssectional thickness of the facing layer.The transition zone between the opposed faces 15 and 17 is characterizedby a decreasing concentration of the respective fiber type from the faceat which it predominates to the opposite face of the product. Face 15preferably is comprised of a greater amount by weight of textile lengthfibers and a lesser amount by weight of short cellulosic fibers (ascompared with the overall concentration of these fibers) interspersedand blended therewith; with face 17 preferably being comprised of agreater amount by weight of short cellulosic fibers and a lesser amountby weight of textile length fibers (as compared to the overallconcentration of these fibers) interspersed and blended therewith.

The overall concentration of textile length fibers within facing layer16 may vary from about 2 to about 50 percent, preferably from about toabout 40 percent. The textile length fibers may, for example, be 1.5denier rayon fibers uniformly cut to 1% inches in length, although thepresent invention is not limited to any specific textile length fiber orconcentration thereof. For example, in facing layers with the overallconcentration of textile length fibers being from about 10 to about 40percent by weight,it has been found that the concentration of textilelength fibers at face is about 5 to percent by weight higher than theoverall concentration. In a specific embodiment of facing layer l6,whichhad an overall composition of about percent by weight rayon fibers andabout 75 percent by weight short cellulosic fibers, the concentration ofrayon fibers at face 15 was approximately -40 percent, and the textilelength fibers were substantially uniformly blended with 65-60 percent ofshort cellulosic fibers. In this last-mentioned facing layer embodiment,approximately 5-10 percent of rayon fibers were present at face 17, andwere in uniform admixture with about 95-90 percent of short cellulosicfibers.

Facing layers suitable for use in this invention have fabric weights inthe range of 1 to 5 oz/ydF, and most preferably within the range of 1.75to about 2.75 oz./yd. The present invention also contemplates thatfabric having an even lower fabric weight may be provided. Afterformation, the web is treated with a bonding agent, such as aself-cross-linking acrylic emulsion, and the facing web is treated witha wetting agent to partially conteract the water repellency of thebonding agent and bring the facing layer to the desired degree ofwettability. One bonding agent which has been employed with considerablesuccess is a latex of polyethylacrylate copolymer containing smallamounts of acrylonitrile and a cross-linking monomer sold under thetrademark HYCAR 2600 X 120. The bonding agent should preferably be ofthe low viscosity type with a viscosity less than 5centipoises. To avoidexcessive water repellency, a surfactant, preferably an anionicsurfactant, is included in the binder suspension. A typical surfactantwhich has been found to be suitable is the ionic sulfonated alkyl estersold under the trademark TRI- TON GR-S. A non-ionic surfactant may alsobe used, and a polyoxyethylene sorbitan monolaurate sold under thetrademark TWEEN 20 has been found to be particularly useful. In atypical application, the binder suspension is controlled to give thefabric a dry solds 1 add on in the range of from about 4% to 9 percentbased on the fabric weight, of which from about 0.15 to about 0.30percent is the amount of surfactant. In facing layers having anextremely low percentage of textile length fibers, such as in facinglayers approaching 2 percent textile length fibers, the binder amountwould be toward the high side of the above-mentioned range. It will beunderstood that the above-mentioned surfactants moderate and reduce thewater repellency which may be imparted to the short and long fibers ofthP web by the bonding agent which bonds them into an integral layer.After treatment with a wetting agent, the facing layer is receptive topenetration by urine but remains less wettable than the batt.

The body of batt 14 is substantially more wettable than the facing layerand tends to draw liquid away from the facing layer. The individualfibers of the batt are extremely wettable, generally having liquid-fibercontact angles below about 15 percent and approaching zero in theoptimum embodiment, as described in detail in the above-mentionedpatent. The wickability, or preferential absorptivity of the body of thebatt for water is limited, however, by its low density which results ina large effective capillary radius for the capillaries between adjacentfibers.

The relative wickability between facing layer 16 and the body of batt 14is affected by both the relative densities of the layers and therelative wettability of the individual fibers in each layer. The facinglayer is sometimes more dense than the body of the batt, tending toprovide greater wickability in the facing layer, but even then theindividual fibers of the batt have substantially smaller liquid-fibercontact angles than those of the facing layer, overcoming the densitydifference and providing a substantial overall increase in capillarypressure to absorb liquid into the body of the batt.

Densified fiber layer 18 of the batt provides the maximum capillarypressure because it combines the very low contact angle of the fibers ofthe batt with the high density (small capillary radius) of the densifiedfibers.

When urine is voided into an area in facing layer 16, it partially wetsthe facing layer and is absorbed therein, spreading out to a limitedextent to form a roughly circular wetted zone therein. When the urinepasses through the facing layer and comes into contact with the body ofbatt 14, it is preferentially absorbed into the body of the batt becauseof the enhanced wettability thereof. It spreads within the body of thebatt to wet a roughly circular zone therein that is slightly larger thanthe wetted zone in facing layer 16. When the urine passes through thebody of the batt it initially contacts one or more of the thickeneddensified lines 19 and the urine is strongly drawn into the densifiedlayer 18 because of its high density and is spread laterally through amuch larger zone, or to the edges of the batt, depending on the amountof urine passed. the urine is transported rapidly along lines 19, morerapidly than it is transported transversely across the densifiedbridging portions between lines, with the result that the roughlycircular zone in the initially wetted loosely compacted portion of thebatt is distorted into a roughly oval zone in the densified portion ofthe batt.

The urine is transported relatively rapidly in all directions of thedensified layer 18 because the densified layer is continuous over oneface of the absorbent panel. However, the thickened portions 19 providefor an increased volumetric flow rate in the longitudinal direction torapidly move a larger volume toward the ends of the absorbent structure.The bridging portions provided by the portions of the densified layerbetween the thickened portions rapidly transport the liquid away fromthe initially wetted area of the densified layer and into contact withpreviously unwetted thickened portions, with the result that liquid israpidly drawn away from the initially wetted area and transported bothlongitudinally and transversely into substantially all portions of thedensified layer.

On occasions when a substantial amount of urine has been voided, thedensified layer becomes saturated and excess urine, aided by thepresence of impervious sheet 12 and its adherence to the densified layerin a discontinuous pattern substantially throughout the interfacetherebetween, flows into the previously dry portions of the body of thebatt, and finally into the previously dry portions of the facing layer.It is to be noted, however, that such flow from a saturated densifiedlayer is from the outermost portions of the diaper inward so that mostof the facing layer remains dry until all other fibrous portions of thediaper are saturated. The thickened densified portions provide for anincreased crosssectional area in the absorbent panel, as compared to adensified layer of uniform thickness or a plurality of spaced densifiedzones, with th greater cross-sectional area providing a capacity to asorb an increased volume of urine. Thus, with the structure of thepresent invention more urine can be stored in the densified layer, andthe tendency for urine to flow back into the batt or into the facinglayer is resisted.

The densified layer of the batt, for the reasons explained above,creates a high capillary pressure which tends to move liquid awayrapidly from the area of the original wetting. However, the speed ofliquid migration is limited in the densified layer because of theresistance provided by its small capillaries. The composite batt used inthis invention, with its densified layer in intimate contact withabsorbent material of lesser density, provides improved speed of liquidmigration over either the densified layer alone, or the uncompressedlayer alone.

It is to be noted that the facing layer as assembled into the diaper iscoterminous with the impervious sheet and there is no folding over ofthe impervious sheet to envelope any edgeof fibrous material. Thus thereis no portion of the upper surface of the diaper which is covered withany plastic material, and no plastic material comes into direct contactwith the infants skin when the diaper is affixed in position by pins ortabs. Prolonged direct contact of plastic material with an infants skincan cause irritation and infection but, nonetheless, is employed inprior art disposable diapers to provide an impervious seal to theinfants skin. The superior absorptive capacity of the diaper of thisinvention and its superior functioning made such plastic-toskin contactunnecessary.

The diaper of this invention is normally packaged and sold in a foldedcondition as described in the abovementioned patent. Briefly, the sidemargins 12b and 16b of the impervious sheet 12 and the facing web 16,together with a portion of batt 14, are folded inwardly in a first foldto provide as the uppermost layer of the fold, a portion of the moistureimpervious sheet. This sub-assembly is then folded outwardly along eachedge in a second fold to cover the first folded portion and to exposethe edge portion of the facing web as the upper layer of the doublefold. In the preferred embodiment, each double fold at the edge of thediaper comprises approximately one-third of the resulting transversedimension of the folded diaper, leaving approximately one-third of thewidth of the folded diaper as a central unfolded and uncovered portion.

The diaper is held in its folded condition by two small central spots ofadhesive applied between the main body of the diaper and the overlyingsides 16b of the facing web, one spot on each folded side of the diaper.

When the diaper is to be put on the infant, the folds are opened on oneside of each of the adhesive spots, and the open portion of the diaperis put under the infants buttocks while the folded portion is raisedinto the crotch region. The final form of the diaper is shown inperspective on a reduced scale in FIG. 3. In one form of the invention,as illustrated in FIG. 3, the diaper is provided with adhesive tabs 26,each having a fixed end secured to the impervious sheet 12 and a freeend wherein the adhesive surface is covered with a facing sheet. Thefacing sheets are removed to expose the adhesive surfaces when thediaper is applied to the infant, as in the configuration shown in FIG.4, and the free ends of the adhesive tabs are secured to oppositecorners of the diaper.

Suitable fibrous structures for making the pads or batts 14 used in thisinvention are made from short cellulosic fibers obtained by the grindingor comminution of compacted wood pulp fibers or cotton linters. Thebatts are initially formed by air blowing the cellulosic fibers onto asupport at a total weight of about 2 to about 10 oz./yd. and thensubjecting the air blown fibers to heavy compression. The densecompacted paper-like layer or skin is prepared by moistening a surfaceof the cellulosic batt with a fine spray of water, and then subjectingthe moistened batt to pressure. The formation of the densified skin onthe cellulosic batt is believed to be due to the formation of stronghydrogen bonds between contacting moistened fibers, similar to the bondsbetween the fibers in paper. By the proper selection of the amount ofmoisture applied to the surface of the batt and by the proper selectionof degree of compression imposed, the properties of the densified skinmay be varied as desired. The thickness, density, strength and othercharacteristics of the densified skin will depend upon the unformity bywhich the moisture is applied, the depth to which it penetrates, and thedegree to which the fibers are compressed. For example, by finelyspraying about 0.0015 cc. of water per square centimeter of web surfaceand then exposing the web to a pressure of about 40 lbs./in. a suitabledensified, coherent paper-like skin 18 is obtained on the surface of theweb which has been moistened. The thickened densified portions 19 may beobtained by subjecting the web to additional pressure, as by the use ofan embossing roll, while the web is still moist, and the additionalpressure is preferably several times higher than the pressure that isapplied to form the densified layer 18.

The short fibers used in making batt 14 of this invention are generallyentirely fibers of wood pulp or cotton linters. however, othercellulosic fibers may be used as well as blends of cellulose fibers withother fibers such as silk, wool, nylon and cellulose acetate. Highlypurified kraft paper pulp fibers have proven to be most satisfactory formost applications.

The diaper of this invention may be assembled in equipment such as thatschematically shown in FIG. 4. A roll of compacted wood pulp 41 isprovided to feed a source of short cellulosic fibers to grinding mill 42from which a stream of fibers is blown onto belt 43 as a layer 44weighing between about 2 and about 10 oz./yd. the air blown layer ispassed under compacting roll 46 from which it emerges with enoughintegrity to sustain itself as a web without the support of belt 43. Theweb then passes through a pair of calender rolls 47 for furthercompression and then under nozzle 48 which deposits at, fine spray ofmoisture on the upper surface of the web. the moistened web then passesbetween another set of calender rolls 49 which exert heavy pressure onit to form a skin 51 on its upper surface.-

The amount of moisture applied to the web may vary suitably from about0.0005 to about 0.03 cc. of water per square centimeter of web surface,depending on the thickness of the paper-like densified skin desired,with lesser amounts of moisture being used for thinner webs and verythin, paper skins and greater amounts for thicker webs and skins ofgreater thickness.

the amount of pressure applied by rolls 49 may vary from about to about100 or more lbs./in. with the commercially preferable range being fromabout 10 to about 50 lbs./in. In a typical embodiment, the web issprayed with about 0.0015 cc. of water per square centimeter of websurface and subjected to a pressure of about 10 lbs. lin f teasers adensi fi ed, asherem pa ery skin of uniform thickness on the surface ofthe web which has been moistened. The amount of moisture is selected sothat the web is still moist following formation of the skin 51. the webthen passes between an embossing roll 52 and a back up roll 53 forformation of the thickened densified portions 19. Roll 52 has aplurality of axially spaced, circumferentially extending riblikeprojections 54 that bear upon the previously formed ,skin 51, andbecause of the residual moisture in the web and the increased pressureapplied by projections 54, thickened densified portions 19 are produced.

The pressure applied by the projections 54 on the embossing roll alsoproduces recesses or air gaps 20 (FIG. 2) in alignment with thickenedportions 19. As is evident from FIG. 2, the unthickened portions of thedensified layer 18 merge with the loosely compacted batt 14 at agenerally planar interface 21, and the thickened densified portionsextend beyond interface 21 and into the loosely compacted batt 18 togive the absorbent panel a three dimensional strengthening effect.

After the skin and the thickened portions are formed, the absorbent webcomes into contact with a web of facing material 55 and is supportedthereby while being cut by cutter 56 into individual batts l4.Polyethylene film 12 is fed to the assembly from roll 58, lines ofadhesive being applied from applicator 59. As described above, theadhesive is applied as parallel lines or beads between the impervioussheet and the densified layer of the batt (or the facing layer in themarginal portion of the diaper). Adhesive may, if desired, be applied asa continuous layer between the polyethylene and the batt, but suchapplication tends to provide excessive stiffness. The adhesive may alsobe applied in other patterns, such as spaced dots or other forms ofso-called island" bonds, but fairly close overall adhesion between thesheet and the batt is required and no portion of the polyethylene shouldbe more than about 2 inches from a point of adhesion. In the absence ofsuch close overall adhesion, the polyethylene film may be separated fromthe densified layer to create substantial spaces in which uncontrollablylarge amounts of free liquid urine can accumulate.

After the facing material and polyethylene are brought into contact withopposite faces of the absorbent batts, the assembly is subjected tocompression by rolls 60 and 61 to shape the diaper assembly, and theindividual diapers are cut off by cutter 62.

If desired, adhesive applicator 59 may be omitted and adhesion betweenthe polyethylene layer and the fibrous layers may be achieved by heatsealing, employing a suitable sealing element in the production line.

The facing layer, as described above, is preferably formed in accordancewith the process disclosed in the above-mentioned Ruffo et alapplication. The facing layer has an overall concentration of from aboutbetween 50 and 98 percent by weight of shortfibers, not exceeding aboutone-fourth inch in length. The average short fibers are from aboutone-sixteenth to about three-sixteenths inch in length. The facing layeris prepared by first feeding a supply of short cellulosic fibers and asupply of textile length fibers 71 to a fiber opening and mixingapparatus 72, which take the form of two individual rotating lickerinsas described in the above-mentioned Ruffo et al application. The fibers70 and 71 are fed to the opening means 72 at a desired rate to provide aweb 73 with a desired overall fiber concentration, and apparatus 73, inaddition to opening the fiber source and individualizing the fibers,also suspends the fibers from each source in separate gaseous streamswhich are impelled toward one another and combined to form a singlecarrier stream wherein the fibers from each separate stream cross overone another to form the facing layer as described above.

The volume ratio of gas to fiber in each of the separate gaseous streamsdepends on the type and length of fibers. Thus, for example, for mostcommercially available shorter type fibers usable in the facing layer ofthe present invention, larger volume ratios may be employed as comparedto the use of staple or longer length fibers where higher volume ratiosare desirably employed. With shorter fibers, the volume ratio of gas tofiber in the separate gaseous stream is at least l2,000:l to l5,000:land up to 275,00011. With the longer or textile length fibers, thevolume ratio of gas to fiber in the separate gaseous stream preferablyhas a minimum of from about l5,000:1 to l8,000:l and up to 275,000:1(desirably between 100,000:l to 275,000:). The minimum gas to fibervolume ratio in the combined stream depends to some extent on theoverall concentration of short and long fibers, and preferably will beequal to or above the minimum ratios set forth above. With gas to fibervolume ratios of between about 12,0002] to about 275,000:1 in thecombined stream, highly uniform webs (see the definition in the Ruffo etal application) can be produced at a high production rate up to 550 feetper minute, or greater. As noted above, the transition in fiberconcentration from face 15 to face 17, and vice versa, is substantiallyuniform. The term substantially uniform, as used herein, is intended tomean that at any point between the opposed faces there is substantiallyno clear cut or distinct line of demarcation between the fibers of thefabric, when the fabric is viewed in cross section.

The web 73 emerging from apparatus 72 may be carried by a conveyor 74 toa bonding station when it is through bonded by a bonding agent of thetype described above from source 75. the web is then dried by passingaround drying drums 76, and then passes upwardly, as shown schematicallyin FIG. 4, where it is bonded to the remainder of the diaper structure.

It will be understood by those skilled in the art that variations andmodifications of the specific embodiments described above may beemployed without de-' parting from the scope of the invention as definedin the appended claims.

what is claimed is:

l. A multi-layer diaper comprising: a porous facing layer in the form ofa nonwoven web formed of staple length fibers and short cellulosicfibers at an overall concentration of staple length fibers from about 25to about 55 percent by weight and an overall concentration of shortfibers from about 45 to about 98 percent by weight, said web having anouter major face characterized by a concentration of staple lengthfibers in excess of said overall concentration and an inner major facecharacterized by a concentration of short cellulosic fibers in excess ofsaid overall concentration; a highly porous, loosely compacted,cellulosic fibrous batt in face-to-face juxtaposition with the innerface of said facing layer; and a water-impervious backing sheet adheredto the outer surface of said batt.

2. A diaper as set forth in claim 1 wherein said staple length fibersare rayon fibers.

3. A diaper as set forth in claim 1 wherein said staple length fibersare polyester fibers.

4. A diaper as set forth in claim 1 wherein said staple length fibersare present at an overall concentration from about to about 40 percentby weight and are present at said outer major face in a concentration offrom about 5 to 20 percent by weight higher than said overallconcentration.

5. A multi-layer diaper comprising: a porous facing layer in the form ofa nonwoven web formed of staple length fibers and short cellulosicfibers at an overall concentration of staple length fibers from about 2to about 55 percent by weight and an overall concentration of shortfibers from about 45 to about 98 percent by weight, said web having anouter major face characterized by a concentration of staple lengthfibers in excess of said overall concentration and an inner major facecharacterized by a concentration of short cellulosic fibers in excess ofsaid overall concentration, the intermediate portion of said web betweensaid faces being characterized by a transition whereby the concentrationof said staple length fibers gradually decreases from said outer majorface to said inner major face and the concentration of said shortcellulosic fibers gradually decreases from said inner major face to saidouter major face; a highly porous, loosely compacted, cellulosic fibrousbatt in face-to-face juxtaposition with the inner face of said facinglayer; and a water-impervious backing sheet adhered to the outer surfaceof said batt.

6. A diaper as set forth in claim 5 wherein said staple length fibersare present at an overall concentration from about 10 to about 40percent by weight and are present at said outer major face in aconcentration of from about 5 to 20 percent by weight higher than saidoverall concentration.

7. A diaper as set forth in claim 6 wherein the transition of each typeof fibers between said faces is substantially uniform.

8. A diaper as set forth in claim 5 wherein said staple length fibersare rayon fibers.

9. A diaper as set forth in claim 5 wherein said staple length fibersare polyester fibers.

10. A multi-layer diaper comprising: a porous facing layer in the formof a nonwoven web formed of staple length fibers and short cellulosicfibers at an overall concentration of staple length fibers from about 2to about 55 percent by weight and an overall concentration of shortfibers from about 45 to about 98 percent by weight, said web having anouter major face characterized by a blend of staple length fibers andshort cellulosic fibers with the concentration of staple length fibersbeing in excess of said overall concentration, and said web having aninner major face characterized by a blend of short cellulosic fibers andstaple length fibers with the concentration of short cellulosic fibersbeing in excess of said overall concentration, the intermediate portionof said web between said faces being characterized by a transitionwhereby the concentration of said staple length fibers graduallydecreases from said outer major face to said inner major face and theconcentration of said short cellulosic fibers gradually decreases fromsaid inner major face to said outer major face; a highly porous, looselycompacted, cellulosic fibrous batt in face-to-face juxtaposition withthe inner face of said facing layer; and a water-impervious backingsheet adhered to the outer surface of said batt.

W105? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,7 Dated October 30,1973

Inventor(s) Frederick Mesek and Virginia Repke It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column line 62, "cores" should read cross Column 6, line 1, "thP" shouldread the Column 9, line 11, "paper skins" should read papery skinsColumn 10, line 2, "275,ooo:)"- should read 275,oo0;1).---.

Column ll, me 7, "25" should read 2% Signed and sealed this 16th, day ofApril 1972 (SEAL) Attest:

EDWARD I'LFLETGHERJR. MARSHALL DANN Attesting Officer Commissioner of"Patents

2. A diaper as set forth in claim 1 wherein said staple length fibersare rayon fibers.
 3. A diaper as set forth in claim 1 wherein saidstaple length fibers are polyester fibers.
 4. A diaper as set forth inclaim 1 wherein said staple length fibers are present at an overallconcentration from about 10 to about 40 percent by weight and arepresent at said outer major face in a concentration of from about 5 to20 percent by weight higher than said overall concentration.
 5. Amulti-layer diaper comprising: a porous facing layer in the form of anonwoven web formed of staple length fibers and short cellulosic fibersat an overall concentration of staple length fibers from about 2 toabout 55 percent by weight and an overall concentration of short fibersfrom about 45 to about 98 percent by weight, said web having an outermajor face characterized by a concentration of staple length fibers inexcess of said overall concentration and an inner major facecharacterized by a concentration of short cellulosic fibers in excess ofsaid overall concentration, the intermediate portion of said web betweensaid faces being characterized By a transition whereby the concentrationof said staple length fibers gradually decreases from said outer majorface to said inner major face and the concentration of said shortcellulosic fibers gradually decreases from said inner major face to saidouter major face; a highly porous, loosely compacted, cellulosic fibrousbatt in face-to-face juxtaposition with the inner face of said facinglayer; and a water-impervious backing sheet adhered to the outer surfaceof said batt.
 6. A diaper as set forth in claim 5 wherein said staplelength fibers are present at an overall concentration from about 10 toabout 40 percent by weight and are present at said outer major face in aconcentration of from about 5 to 20 percent by weight higher than saidoverall concentration.
 7. A diaper as set forth in claim 6 wherein thetransition of each type of fibers between said faces is substantiallyuniform.
 8. A diaper as set forth in claim 5 wherein said staple lengthfibers are rayon fibers.
 9. A diaper as set forth in claim 5 whereinsaid staple length fibers are polyester fibers.
 10. A multi-layer diapercomprising: a porous facing layer in the form of a nonwoven web formedof staple length fibers and short cellulosic fibers at an overallconcentration of staple length fibers from about 2 to about 55 percentby weight and an overall concentration of short fibers from about 45 toabout 98 percent by weight, said web having an outer major facecharacterized by a blend of staple length fibers and short cellulosicfibers with the concentration of staple length fibers being in excess ofsaid overall concentration, and said web having an inner major facecharacterized by a blend of short cellulosic fibers and staple lengthfibers with the concentration of short cellulosic fibers being in excessof said overall concentration, the intermediate portion of said webbetween said faces being characterized by a transition whereby theconcentration of said staple length fibers gradually decreases from saidouter major face to said inner major face and the concentration of saidshort cellulosic fibers gradually decreases from said inner major faceto said outer major face; a highly porous, loosely compacted, cellulosicfibrous batt in face-to-face juxtaposition with the inner face of saidfacing layer; and a water-impervious backing sheet adhered to the outersurface of said batt.